U.S. patent application number 15/451422 was filed with the patent office on 2017-09-28 for light modulator.
The applicant listed for this patent is CENTERA Photonics Inc.. Invention is credited to Chao-Hsuan CHUANG, Chien-Chen HSIEH.
Application Number | 20170276970 15/451422 |
Document ID | / |
Family ID | 59897963 |
Filed Date | 2017-09-28 |
United States Patent
Application |
20170276970 |
Kind Code |
A1 |
CHUANG; Chao-Hsuan ; et
al. |
September 28, 2017 |
LIGHT MODULATOR
Abstract
A light modulator includes a substrate, a first semiconductor
structure, a second semiconductor structure and a dielectric
structure. The substrate has a principal surface and a first
direction substantially perpendicular to the principal surface. The
first semiconductor structure has a first conductive type and
disposed over the principal surface. The second semiconductor
structure has a second conductive type and disposed over the
principal surface, in which the second semiconductor structure is
free from overlapping the first semiconductor structure in the
first direction. The dielectric structure is disposed over the
principal surface and extends upwards from the principal surface
such that dielectric structure is interposed between the first
semiconductor structure and the second semiconductor structure.
Inventors: |
CHUANG; Chao-Hsuan; (Hsinchu
County, TW) ; HSIEH; Chien-Chen; (Hsinchu,
TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CENTERA Photonics Inc. |
Hsinchu |
|
TW |
|
|
Family ID: |
59897963 |
Appl. No.: |
15/451422 |
Filed: |
March 7, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02F 1/025 20130101 |
International
Class: |
G02F 1/025 20060101
G02F001/025 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 28, 2016 |
TW |
105109703 |
Claims
1. A light modulator, comprising: a substrate having a principal
surface and a first direction substantially perpendicular to the
principal surface; a first semiconductor structure, having a first
conductive type, positioned over the principal surface; a second
semiconductor structure, having a second conductive type,
positioned over the principal surface, wherein the first
semiconductor structure is free from overlapping the second
semiconductor structure in the first direction; and a dielectric
structure positioned over the principal surface and extending
upwards along the first direction from the principal surface, the
dielectric structure being interposed between the first
semiconductor structure and the second semiconductor structure;
wherein the first semiconductor structure, the second semiconductor
structure, and the dielectric structure constitute an optical
waveguide for providing a substantially elliptical or circular
light channel.
2. The light modulator according to claim 1, wherein the first
semiconductor structure and the second semiconductor structure
respectively have a first top surface and a second top surface, and
the first top surface and the second top surface are not covered by
the dielectric structure.
3. The light modulator according to claim 2, wherein the first top
surface of the first semiconductor structure laterally extends on a
substantially identical first level to a position touching the
dielectric structure.
4. The light modulator according to claim 3, wherein the second top
surface of the second semiconductor structure extends on a
substantially identical second level to a position touching the
dielectric structure.
5. The light modulator according to claim 4, wherein the first
level is substantially the same as the second level.
6. The light modulator according to claim 1, wherein the dielectric
structure separates the first semiconductor structure from the
second semiconductor structure such that the first semiconductor
structure is not in direct contact with the second semiconductor
structure.
7. The light modulator according to claim 1, wherein the dielectric
structure has a width and a height that is greater than the
width.
8. The light modulator according to claim 7, wherein the height of
the dielectric structure is substantially equal to a thickness of
the first semiconductor structure and a thickness of the second
semiconductor structure.
9. The light modulator according to claim 1, wherein the first
semiconductor structure and the second semiconductor structure
respectively have a first width and a second width, and the first
width is substantially equal to the second width.
10. The light modulator according to claim 1, wherein the first
semiconductor structure comprises a first doping portion and a
second doping portion, the first doping portion being in contact
with the dielectric structure and located between the dielectric
structure and the second doping portion, wherein a doping
concentration of the first doping portion is less than a doping
concentration of the second doping portion.
11. The light modulator according to claim 10, wherein a height of
the first doping portion is greater than a height of the second
doping portion.
12. The light modulator according to claim 10, wherein the first
doping portion comprises a standing portion and an extending
portion, the standing portion being in contact with the dielectric
structure, wherein the extending portion laterally extends from the
standing portion to the second doping portion, and a height of the
standing portion is greater than a height of the extending
portion.
13. The light modulator according to claim 12, wherein the height
of the standing portion substantially equals a height of the
dielectric structure, and the height of the extending portion
substantially equals a height of the second doping portion.
14. The light modulator according to claim 10, wherein the second
semiconductor structure comprises a fourth doping portion and a
fifth doping portion, the fourth doping portion being in contact
with the dielectric structure and positioned between the dielectric
structure and the fifth doping portion, wherein a doping
concentration of the fourth doping portion is less than a doping
concentration of the fifth doping portion.
15. The light modulator according to claim 14, wherein a height of
the fourth doping portion is greater than a height of the fifth
doping portion.
16. The light modulator according to claim 14, wherein the fourth
doping portion comprises a standing portion and an extending
portion, the standing portion being in contact with the dielectric
structure, wherein the extending portion laterally extends from the
standing portion to the fifth doping portion, and a height of the
standing portion is greater than a height of the extending
portion.
17. The light modulator according to claim 16, wherein the height
of the standing portion substantially equals a height of the
dielectric structure, and the height of the extending portion
substantially equals a height of the fifth doping portion.
Description
RELATED APPLICATIONS
[0001] This application claims priority to Taiwan Application
Serial Number 105109703, filed Mar. 28, 2016, the entirety of which
is incorporated herein by reference.
BACKGROUND
[0002] Technical Field
[0003] The present disclosure relates to a light modulator. More
particularly, the present disclosure relates to a light modulator
with a horizontal configuration.
[0004] Description of Related Art
[0005] Optical modulators have been widely applied in a variety of
optical fields. Optical modulators include a variety of types such
as amplitude modulators, phase modulators, polarization modulators
and the likes. The optical phase modulators may be used to control
the phase of light. Typical optical phase modulators, for example,
are electro-optical modulator devices such as Pockels cells or
liquid crystal cell. A variety of optical phase modulators are used
in integrated optical system (i.e., integrated optics). Light is
transmitted in the waveguide structure of the integrated optical
system, and the phase of light is controlled or modulated in the
waveguide structure. In optical fiber communication systems, the
optical phase modulators can be used to transmit coded messages. In
addition, the optical modulators can also be applied in photonic
chips.
SUMMARY
[0006] According to one aspect of the present disclosure, a light
modulator is provided. The light modulator includes a substrate, a
first semiconductor structure, a second semiconductor structure,
and a dielectric structure. The substrate has a principal surface
and a first direction substantially perpendicular to the principal
surface. The first semiconductor structure has a first conductive
type and positioned over the principal surface. The second
semiconductor structure has a second conductive type and positioned
over the principal surface, in which the first semiconductor
structure is free from overlapping the second semiconductor
structure in the first direction. The dielectric structure is
positioned over the principal surface and extends upwards along the
first direction from the principal surface, and the dielectric
structure is interposed between the first semiconductor structure
and the second semiconductor structure. The first semiconductor
structure, the second semiconductor structure, and the dielectric
structure constitute an optical waveguide for providing a
substantially elliptical or circular light channel.
[0007] In some embodiments of the present disclosure, the first
semiconductor structure and the second semiconductor structure
respectively have a first top surface and a second top surface, and
the first top surface and the second top surface are covered by the
dielectric structure.
[0008] In some embodiments of the present disclosure, the first top
surface of the first semiconductor structure laterally extends on a
substantially identical first level to a position touching the
dielectric structure.
[0009] In some embodiments of the present disclosure, the second
top surface of the second semiconductor structure extends on a
substantially identical second level to a position touching the
dielectric structure.
[0010] In sonic embodiments of the present disclosure, the first
level is substantially the same as the second level.
[0011] In some embodiments of the present disclosure, the
dielectric structure separates the first semiconductor structure
from the second semiconductor structure such that the first
semiconductor structure is not in direct contact with the second
semiconductor structure.
[0012] In some embodiments of the present disclosure, the
dielectric structure has a width and a height that is greater than
the width.
[0013] In some embodiments of the present disclosure, the height of
the dielectric structure is substantially equal to a thickness of
the first semiconductor structure and a thickness of the second
semiconductor structure.
[0014] In some embodiments of the present disclosure, a ratio of
the height to the width of the dielectric structure is ranged from
about 1.0 to about 50.0.
[0015] In some embodiments of the present disclosure, the first
semiconductor structure and the second semiconductor structure
respectively have a first width and a second width, and the first
width is substantially equal to the second width.
[0016] In some embodiments of the present disclosure, the first
semiconductor structure comprises a first doping portion and a
second doping portion. The first doping portion is in contact with
the dielectric structure and located between the dielectric
structure and the second doping portion, and a doping concentration
of the first doping portion is less than a doping concentration of
the second doping portion.
[0017] In some embodiments of the present disclosure, a height of
the first doping portion is greater than a height of the second
doping portion.
[0018] In some embodiments of the present disclosure, the first
doping portion comprises a standing portion and an extending
portion, and the standing portion is in contact with the dielectric
structure. The extending portion laterally extends from the
standing portion to the second doping portion, and a height of the
standing portion is greater than a height of the extending
portion.
[0019] In some embodiments of the present disclosure, the height of
the standing portion substantially equals a height of the
dielectric structure, and the height of the extending portion
substantially equals a height of the second doping portion.
[0020] In some embodiments of the present disclosure, the second
semiconductor structure comprises a fourth doping portion and a
fifth doping portion. The fourth doping portion is in contact with
the dielectric structure and positioned between the dielectric
structure and the fifth doping portion. A doping concentration of
the fourth doping portion is less than a doping concentration of
the fifth doping portion.
[0021] In some embodiments of the present disclosure, a height of
the fourth doping portion is greater than a height of the fifth
doping portion.
[0022] In some embodiments of the present disclosure, the fourth
doping portion comprises a standing portion and an extending
portion. The standing portion is in contact with the dielectric
structure. The extending portion laterally extends from the
standing portion to the fifth doping portion, and a height of the
standing portion is greater than a height of the extending
portion.
[0023] In some embodiments of the present disclosure, the height of
the standing portion substantially equals a height of the
dielectric structure, and the height of the extending portion
substantially equals a height of the fifth doping portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Aspects of the present disclosure are best understood from
the following detailed description when read with the accompanying
figures. It is noted that, in accordance with the standard practice
in the industry, various features are not drawn to scale. In fact,
the dimensions of the various features may be arbitrarily increased
or reduced for clarity of discussion.
[0025] FIG. 1 is a cross-sectional view schematically illustrating
a light modulator according to a comparative example of the present
disclosure.
[0026] FIG. 2 is a diagram illustrating a simulation result of a
light intensity distribution of a light modulator according to a
comparative example of the present disclosure.
[0027] FIG. 3 is a perspective view schematically illustrating a
light modulator according to various embodiments of the present
disclosure.
[0028] FIG. 4 is a cross-sectional view schematically illustrating
a light modulator according to some embodiments of the present
disclosure.
DESCRIPTION OF THE EMBODIMENTS
[0029] The following disclosure provides many different
embodiments, or examples, for implementing different features of
the provided subject matter. Specific examples of components and
arrangements are described below to simplify the present
disclosure. These are, of course, merely examples and are not
intended to be limiting. For example, the formation of a first
feature over or on a second feature in the description that follows
may include embodiments in which the first and second features are
formed in direct contact, and may also include embodiments in which
additional features may be formed between the first and second
features, such that the first and second features may not be in
direct contact. In addition, the present disclosure may repeat
reference numerals and/or letters in the various examples. This
repetition is for the purpose of simplicity and clarity and does
not in itself dictate a relationship between the various
embodiments and/or configurations discussed.
[0030] It will be understood that, although the terms first,
second, etc, may be used herein to describe various elements, these
elements should not be limited by these terms. These terms are only
used to distinguish one element from another. For example, a first
element could be termed a second element, and, similarly, a second
element could be termed a first element, without departing from the
scope of the embodiments. As used herein, the term "and/or"
includes any and all combinations of one or more of the associated
listed items.
[0031] Further, spatially relative terms, such as "beneath,"
"below," "lower," "above," "upper" and the like, may be used herein
for ease of description to describe one element or feature's
relationship to another element(s) or feature(s) as illustrated in
the figures. The spatially relative terms are intended to encompass
different orientations of the device in use or operation in
addition to the orientation depicted in the figures. The apparatus
may be otherwise oriented (rotated 90 degrees OT at other
orientations) and the spatially relative descriptors used herein
may likewise be interpreted accordingly.
[0032] It will be understood that when an element is referred to as
being "connected" or "coupled" to another element, it can be
directly connected or coupled to the other element or intervening
elements may be present. In contrast, when an element is referred
to as being "directly connected" or "directly coupled" to another
element, there are no intervening elements present.
[0033] FIG. 1 is a cross-sectional view schematically illustrating
a light modulator 10 according to a comparative example of the
present disclosure. The light modulator 10 mainly includes a p-type
polycrystalline silicon layer 11, an N-type polycrystalline silicon
layer 12, an oxide layer 13, a conductive contact structure 14, a
conductive contact structure 15 and a substrate 17. The p-type
polycrystalline silicon layer 11 includes a P+ region 11a and a P
region 11b. The N-type polycrystalline silicon layer 12 includes an
N+ region 12a and an N region 12b. The conductive contact structure
14 and conductive contact structure 15 respectively contact the P+
region 11a and the N+ region 12a. The p-type polycrystalline
silicon layer 11 is overlapped with a portion of the N-type
polycrystalline silicon layer 12. The oxide layer 13 is interposed
between the overlapped portions of the p-type polycrystalline
silicon layer 11 and the N-type polycrystalline silicon layer 12.
The overlapped regions of the p-type polycrystalline silicon layer
11, the oxide layer 13, and the N-type polycrystalline silicon
layer 12 constitute an active region 16 of the light modulator 10.
It is noted that the p-type polycrystalline silicon layer 11, the
oxide layer 13, and the N-type polycrystalline silicon layer 12 in
the active region 16 are configured to stack in a perpendicular
direction to the substrate 17. Furthermore, the p-type
polycrystalline silicon layer 11 and the N-type polycrystalline
silicon layer have to be laterally extended for the purpose of
disposing the conductive contact structures 14 and 15.
[0034] The oxide layer 13 may be understood or referred to as a
"gate dielectric". When an electrical potential difference is
applied between the p-type polycrystalline silicon layer 11 and the
N-type polycrystalline silicon layer 12, free carriers 18 gathers
at the opposite sides of the oxide layer 13. When light transmits
in the active region 16 along a direction 19 that is perpendicular
to the illustrated paper sheet, the gathered free carriers 18
changes the phase of the light, thereby constituting the light
modulator 10 capable of altering the phase of the light.
[0035] According to the operating principle of the light modulator
10 described above, the light transmitted therein is desirably to
be concentrated or collected in the active region 16 in order to
avoid the light escaping to the outside of the active region 16,
and therefore the light modulator 10 may provide a relatively
better performance.
[0036] FIG. 2 is a diagram illustrating a simulation result of the
light intensity distribution of the light modulator 10. In FIG. 2,
it may be observed that light intensity distribution is deformed
and distorted by the p-type polycrystalline silicon layer 11 and
the N-type polycrystalline silicon layer 12. The light intensity
distribution shows a laterally extension (or diffusion) along the
p-type polycrystalline silicon layer 11 and the N-type
polycrystalline silicon layer 12, resulting in that the light can
not be completely concentrated in the active region.
[0037] In one aspect, it is desired to gather more free carriers at
opposite sides of the oxide layer 13 in order to more effectively
alter the phase of the light. In another aspect, however, it is not
desired to have high doping concentrations at opposite sides of the
oxide layer 13 because the dopants obstruct or hinder the light
transmission. Therefore, there exists a trade-off there
between.
[0038] Accordingly, the light modulator 10 has two technical
drawbacks. One of the drawbacks is the light intensity distribution
being distorted, resulting in that the light can not be effectively
concentrated in the active region. The other one of the drawbacks
is the dopant concentration at opposite sides of the oxide layer 13
is difficult to be controlled or modulated to reduce the hindrance
to light transmission.
[0039] According to the founding and research described above, the
inventor of the present disclosure provides various embodiments of
the present disclosure to resolve the drawbacks of the light
modulator 10. FIG. 3 is perspective view schematically illustrating
a light modulator 100 according to various embodiments of the
present disclosure. The light modulator 100 includes a substrate
110, a first semiconductor structure 120, a second semiconductor
structure 130 and a dielectric structure 140. One of the technical
points of the present disclosure is that the structure of the light
modulator 100 is changed in which a relatively higher dopant
concentration is provided in the region far away from the
dielectric structure 140 to promote a relatively greater amount of
free carriers to be generated at opposite sides of the dielectric
structure 140; however, a relatively lower dopant concentration is
provided in the region adjacent to the dielectric structure 140 to
effectively reduce the hindrance to light transmission.
[0040] The substrate 110 has a principal surface 112 and a first
direction D1 substantially perpendicular to the principal surface
112. In one embodiment, the substrate 110 includes a doped or
undoped silicon wafer, or a semiconductor-on-insulator substrate,
or other liked semiconductor materials.
[0041] The first semiconductor structure 120 is positioned over the
principal surface 112, and the first semiconductor structure 120
has a first conductive type. For example, the first semiconductor
structure 120 may include N-type semiconductor material or P-type
semiconductor material. Illustrative examples of the first
semiconductor structure 120 include N-doped or P-doped
polycrystalline silicon, amorphous silicon, single crystalline
silicon, or the like. The dopants, for example, may be Group 3A or
Group 5A element or compounds containing Group 3A or 5A group
elements, or the like.
[0042] The second semiconductor structure 130 is positioned over
the principal surface 112, and the second semiconductor structure
130 has a second conductive type. It is noted that the second
semiconductor structure 130 is not overlapped With the first
semiconductor structure 120 in the first direction D1. In
particular, when viewed in the first direction D1 (e.g., the
diagram shown in FIG. 3), there exists a spacing interval between
the second semiconductor structure 130 and the first semiconductor
structure 120, and therefore the second semiconductor structure 130
is not overlapped with the first semiconductor structure 120. In
addition, the second conductive type of the second semiconductor
structure 130 is different from the first conductive type of the
first semiconductor structure 120. For example, when the first
semiconductor structure 120 includes N-type semiconductor material,
the second semiconductor structure 130 includes P-type
semiconductor material; alternatively when the first semiconductor
structure 120 includes P-type semiconductor material, the second
semiconductor structure 130 includes N-type semiconductor
material.
[0043] The dielectric structure 140 extends upwards from the
principal surface 112 of the substrate 110 along the first
direction D1, and is interposed between the first semiconductor
structure 120 and the second semiconductor structure 130. In some
embodiments of the present disclosure, the first semiconductor
structure 120 has a first sidewall 120S, and the second
semiconductor structure 130 has a second sidewall 130S. In certain
examples, the first sidewall 120S and the second side wall 130S
extend substantially along the first direction D1, and the first
sidewall 120S is opposite to the second side wall 130S. The
dielectric structure 140 is interposed between the first side wall
120S of the first semiconductor structure 120 and the second side
wall 130S of the second semiconductor structure 130, and therefore
physically separates the first semiconductor structure 120 from the
second semiconductor structure 130 such that the first
semiconductor structure 120 is not in direct contact with the
second semiconductor structure 130.
[0044] The dielectric structure 140 may be any suitable dielectric
material such as silicon nitride, silicon oxide, doped silicon
glass, or the like. The dielectric structure 140 may include a
low-k dielectric material such as for example phosphorus silicate
glass (PSG), boron phosphorous silica glass (BPSG), fluorine
silicon glass (FSG), silicon carbide material, or a combination
thereof, or the like. The dielectric structure 140 may include
high-k dielectric material such as for example hafnium oxide
(HfO2), hafnium silicon oxide (HfSiO), hafnium silicon oxide
nitrogen (HfSiON), tantalum oxide, hafnium (HfTaO), hafnium oxide
(HfTiO), hafnium, zirconium oxide (HfZrO), or the like.
[0045] In some embodiments of the present disclosure, the,
dielectric structure 140 physically contacts the first
semiconductor structure 120, and the contact surface (or interface)
between the dielectric structure 140 and the first semiconductor
structure 120 extends to the principal surface 112 of the substrate
110. In yet some embodiments, the dielectric structure 140
physically contacts the second semiconductor structure 130, and the
contact surface (or interface) between the dielectric structure 140
and the second semiconductor structure 130 extends to the principal
surface 112 of the substrate 110.
[0046] In some embodiments of the present disclosure, the height H
of the dielectric structure 140 is greater than the width W of the
dielectric structure 140. In some examples, the ratio of the height
H to the width W (i.e., H/W) of the dielectric structure 140 is
ranged from about 1.0 to about 50.0, such as about 1.5, about 2.0,
about 3.0, about 5.0 about 10.0, about 20.0, about 30.0 and about
40.0. In some examples, the height H of dielectric structure 140 is
ranged from about 0.05 .mu.m to about 5 .mu.m, for example about
0.1 .mu.m, about 0.2 .mu.m, about 0.5 .mu.m, about 1 .mu.m, about 2
.mu.m or about 4 .mu.m.
[0047] In some embodiments of the present disclosure, the first
semiconductor structure 120 and the second semiconductor structure
130 respectively have a first top surface 120T and a second top
surface 130T. The first top surface 120T extends laterally on a
substantially identical first level L1 to a position touching the
dielectric structure 140, and the second top surface 130T extends
laterally on a substantially identical level L2 to a position
touching the dielectric structure 140. In some examples, the first
level L1 is substantially the same as the second level L2. That is,
the first top surface 120T of the first semiconductor structure and
the second top surface 130T of the second semiconductor structure
are extended on substantially the same level.
[0048] In some embodiments of the present disclosure, the
dielectric structure 140 is free from coverage on the first top
surface 120T of the first semiconductor structure 120 and the
second top surface 130T of the second semiconductor structure 130.
Therefore, when viewed along the first direction D1, the first
semiconductor structure 120, the dielectric structure 140 and the
second semiconductor structure 130 are not overlapped with each
other. In yet some embodiments, the first semiconductor structure
120 and the second semiconductor structure 130 do not cover the top
surface of the dielectric structure 140.
[0049] In yet some embodiments, the bottom surface 140B of the
dielectric structure 140, the bottom surface 120B of the first
semiconductor structure 120 and the bottom surface 130B of the
second semiconductor structure 130 are in direct contact with the
principal surface 112 of the substrate 110.
[0050] In some embodiments of the present disclosure, when viewed
along the first direction D1, the first semiconductor structure 120
and the second semiconductor structure 130 are mirror symmetric
with respect to the dielectric structure 140 as a symmetry axis. In
some examples, the first semiconductor structure 120 and the second
semiconductor structure 130 respectively have a first width W1 and
a second width W2, and the first width W1 is substantially equal to
the second width W2. In yet some embodiments, in a cross-sectional
structure of the light modulator 100, the first semiconductor
structure 120 and second semiconductor structure 130 appear a
horizontally symmetric structure with respect to the dielectric
structure 140 as a symmetry axis. In some examples, the height H of
the dielectric structure 140 is substantially equal to the
thickness T1 of the first semiconductor structure 120 and the
thickness T2 of the second semiconductor structure 130.
[0051] In some embodiments of the present disclosure, the first
semiconductor structure 120, the second semiconductor structure 130
and the dielectric structure 140 of the light modulator 100 are
disposed laterally on the same plane. A spatial set of the first
semiconductor structure 120, the second semiconductor structure 130
and the dielectric structure 140 defines an active region 101 of
the light modulator 100. Even though the light intensity
distribution potentially possesses a lateral extension along the
first and second semiconductor structures, the light is still
confined or limited in the active region 101. Therefore, according
to various embodiments of the present disclosure, light may be
confined in the active region to transmit. In addition, the range
of the active region 101 can be modulated by modifying the
thicknesses and the widths of the first semiconductor structure
120, the second semiconductor structure 130 and the dielectric
structure 140. Accordingly, the technical drawbacks that the light
can not be confined in the active region associated with the light
modulator 10 illustrated in FIG. 1 is effectively resolved in
accordance with the embodiments of the present disclosure.
[0052] According to some embodiments of the present disclosure, the
light intensity distribution 103 exhibits an eclipse-liked
distribution, as shown in FIG. 3. The light transmitted in the
regions adjacent to the dielectric structure 140 has a relatively
higher intensity, whereas the light transmitted in the regions far
away from the dielectric structure 140 has a relatively lower
intensity. In some examples, light intensity distribution 103 is
symmetric with respect to the dielectric structure 140 as a
symmetric axis. According to various embodiments of the present
disclosure, the first semiconductor structure, the second
semiconductor structure, and the dielectric structure constitute an
optical waveguide structure, and that structure provides a light
channel or light intensity distribution which is substantially
elliptical or circular.
[0053] According to yet some embodiments of the present disclosure,
the first semiconductor structure 120 includes a number of doping
regions such as a first doping region 121, a second doping region
122 and a third doping region 123. The dopant concentration of the
first doping region 121 is less than the dopant concentration of
the doping region 122, which is less than the dopant concentration
of the third doping region 123. In other words, in the first
semiconductor structure 120, the first doping region 121 has the
minimum dopant concentration, while the third doping region 123 has
a maximum dopant concentration. Similarly, the second semiconductor
structure 130 may includes a number of doping regions such as a
fourth doping region 131, a fifth doping region 132 and a sixth
doping region 133. The dopant concentration of the fourth doping
region 131 is less than the dopant concentration of the fifth
doping region 132, which is less than the dopant concentration of
the sixth doping region 133. In other words, in the second
semiconductor structure 130, the fourth doping region 131 has a
minimum dopant concentration, while the sixth doping region 133 has
a maximum dopant concentration.
[0054] The maximum dopant concentrations are provided in both of
the third doping region 123 and the sixth doping region 133, that
are positioned far way from the dielectric structure 140, in order
to generate a relatively greater amount of free carriers gathering
at opposite sides of the dielectric structure 140. The minimum
dopant concentrations are provided in both of the first doping
region 121 and the fourth doping region 131 that are adjacent to
the dielectric structure 140. These regions adjacent to the
dielectric structure 140 has a relatively higher intensity of
light, and the reduction of the dopant concentration in this region
may effectively reduce the hindrance to light transmission. In
these embodiments, different doping regions are horizontally
disposed on a plane, and therefore a plurality of regions with
different dopant concentrations may be easily formed by ion
implanting technologies. As compared to the method that the dopant
concentration gradient is constituted in the thickness direction by
ion implanting approach so to form regions with different dopant
concentrations, the embodiments provided in the present disclosure
may achieve the effect of precise control of the concentration
distribution.
[0055] According to some embodiments of the present disclosure, the
summation of the first width W1 of the first semiconductor
structure 120, the width W of the dielectric structure 140, and the
second width W2 of the second semiconductor structure 130 defines
the width Q of the light modulator 100, and the height H of the
dielectric structure 140 defines the thickness T of the light
modulator 100. For example, the width Q of the light modulator 100
may be about 0.2 .mu.m to about 10 .mu.m, and the thickness T of
the light modulator 100 may be about 0.1 .mu.m to about 5
.mu.m.
[0056] In yet some embodiments, the light modulator 100 may further
includes a first conductive contact structure 151 and a second
conductive contact structure 152 respectively in contact with the
first semiconductor structure 120 and the second semiconductor
structure 130. In some examples, the first conductive contact
structure 151 is in contact with the third doping region 123 of the
first semiconductor structure 120, whereas the second conductive
contact structure 152 is in contact with the sixth doping region
133 of the second semiconductor structure 130. The first conductive
contact structure 151 and the second conductive contact structure
152 are configured to apply voltage signals to the first
semiconductor structure 120 and the second semiconductor structure
130 such that a voltage difference is generated between the first
semiconductor structure 120 and the second semiconductor structure
130.
[0057] FIG. 4 is a cross-sectional view schematically illustrating
a light modulator 100a according to some embodiments of the present
disclosure. In FIG. 4, the same or similar features are identified
by the same reference numerals. These features are the same as or
similar to like-numbered features described with respect to FIG. 1.
The first semiconductor structure 120 of the light modulator 100a
includes a first doping portion 121'', a second doping portion
122'' and a third doping portion 123''. The dopant concentration of
the first doping portion 121'' is less than the dopant
concentration of the second doping portion 122'', and the dopant
concentration of the second doping portion 122'' is less than that
of the third doping portion 123''. Similarly, the second
semiconductor structure 130 includes a fourth doping portion 131'',
a fifth doping portion 132'' and a sixth doping portion 133''. The
dopant concentration of the fourth doping portion 131'' is less
than the dopant concentration of the fifth doping portion 132'',
and the dopant concentration of the fifth doping portion 132' is
less than that of the six doping portion 133''. One of the features
of the light modulator 100a is that first doping portion 121'' has
a height that is greater than a height H2 of the second doping
portion 122'', and the fourth doping portion 131'' has a height H3
that is greater than a height H4 of the fifth doping portion
132''.
[0058] In one embodiments, the first doping portion 121'' includes
a standing portion 126 and an extending portion 127. The standing
portion 126 is in contact with the dielectric structure 140, and
the extending portion 127 extends laterally from the standing
portion 126 to the second doping portion 122'. A height H1 of the
standing portion 126 is greater than a height H2 of the extending
portion 127. In some examples, the standing portion 126 and the
dielectric structure 140 have substantially the same height H1,
while the extending portion 127, the second doping portion 122'',
and the third doping portion 123'' have substantially the same
height H2. For example, the height H1 may be about 150 nm to about
300 nm, and the height H2 may be about 50 nm to about 130 nm. In
some examples, a height difference G1 between a top surface of the
first doping portion 121'' and a top surface of the second doping
portion 122'' is about 50% to about 70% of the height H1.
[0059] Similarly, the fourth doping portion 131'' includes a
standing portion 136 and an extending portion 137. The standing
portion 136 is in contact with the dielectric structure 140, and
the extending portion 137 extends laterally from the standing
portion 136 to the fifth doping portion 132''. A height H3 of the
standing portion 136 is greater than a height H4 of the extending
portion 137. In some examples, the standing portion 136 and the
dielectric structure 140 have substantially the same height H3, and
the extending portion 137, the fifth doping portion 132'', and the
sixth doping portion 133'' have substantially the same height H4.
For example, the height H3 may be about 150 nm to about 300 nm, and
the height H4 maybe about 50 nm to about 130 nm. In some examples,
a height difference G2 between a top surface of the fourth doping
portion 131'' and a top surface of the fifth doping portion 132''
is about 50% to about 70% of the height H3. In one specific
example, the height H1 is substantially equal to the height H3, and
the height H2 is substantially equal to the height H4.
[0060] The standing portion 126, the standing portion 136 and the
dielectric structure 140 collectively constitute a rib waveguide of
the light modulator 100a. In some examples, the total width E in
sum of the width E1 of the standing portion 126, the width E2 of
the standing portion 136, and the width E3 of the dielectric
structure 140 is about 1.5 folds to about 2.5 folds of the height
H1 of the standing portion 126 (or the height H3 of the standing
portion 136). The total width E, for example, may be about 400 nm
to about 550 nm, preferably about 410 nm to about 430 nm.
[0061] According to some embodiments of the present disclosure, the
standing portion 126 and the standing portion 136 may confine or
alter the light intensity distribution 103 in the light modulator
100a. As shown in FIG. 4, the light intensity distribution 103 in
the light modulator 100a may be effectively concentrated or limited
in the range of the total width E by the standing portion 126 and
the standing portion 136. In addition, the heights H1, H3 of the
standing portions 126, 136 affect the light intensity distribution
103 as well. By altering the heights H1, H3 of the standing
portions 126, 136, a circle-liked light intensity distribution 103
may be obtained. Therefore, according to some embodiments of the
present disclosure, the features of the widths and/or the heights
of the standing portions and certain ratios provided herein
contribute to certain technical effects, and are not simple design
changes or simple modifications.
[0062] The light modulator 100a may optionally include a dielectric
layer 160, a first conductive contact structure 151 and a second
conductive contact structure 152. The dielectric layer 160 is
positioned over the first semiconductor structure 120, the second
semiconductor structure 130 and the dielectric structure 140. The
dielectric layer 160 has a first opening 161 and a second opening
162 respectively aligned with the third doping portion 123'' and
the sixth doping portion 133''. The first conductive contact
structure 151 and the second conductive contact structure 152 are
electrically connected to the third doping portion 123'' and the
sixth doping portion 133'' respectively through the first opening
161 and the second opening 162.
[0063] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
present disclosure without departing from the scope or spirit of
the present disclosure. In view of the foregoing, it is intended
that the present disclosure cover modifications and variations of
the present disclosure provided they fall within the scope of the
following claims and their equivalents.
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